Using light to automatically analyze or measure a contained sample without physically contacting the sample has been accomplished in cytometry, spectrophotometry, fluorometry and nephelometry. The instruments used to make such measurements and/or analysis are particularly adapted to the sample considered and the specific technique of measurement. The various techniques are well known and are mentioned herein as background relative to the particular apparatus and method disclosed and claimed.
Cytometry evaluates particles or cells passing in a stream through light one at a time and for a brief period of time. Typically five thousand particles or cells pass through the light per second and produce a signal each time the light is interrupted by the passage of a cell or particle. The signals represent scatter or fluorescent emissions. The signals are analyzed with a photomultiplier tube.
Spectrometry identifies a compound by its spectrum as produced by illuminating the compound. Spectrophotometers measure transmittance or reflectance to study those properties of specimens as a function of wavelength. Spectradiometers measure the radiant energy from a source at each wavelength throughout the spectrum. The spectral regions are separated either by calibrated filters or a calibrated monochromator. The detector receives energy from a photomultiplier.
Nephelometric turbidity is an empirical measurement of the light-scattering characteristics (Tyndall effect) of a sample of particulate matter. Intensity of scattered light at ninety degrees to the incident beam of light is measured and numerical values are obtained by comparison with the light-scattering characteristics of a known or an arbitrarily chosen material in an equivalent optical system. Comparison may also be made between transmitted light effect and scattered light effect.
Spectrochemical (spectrographic, spectrometric, spectroscopic) analysis is the determination of the chemical elements in a sample quantitatively or semiquantitatively, by measurements of the wavelength and intensity of spectral lines produced by suitable excitation procedures with a suitable optical dispersion device. The field of spectroanalysis may be subdivided into atomic emission or absorption, molecular emission or absorption, X ray, flame, fluorescent, and other types of instrumental analysis.
Measurement of the dimensions of the components of a sample medium held within a gap between a transparent tube and a cylindrical float is a diagnostic technique used for purposes of analyzing blood samples in a quantitative buffy coat centrifugal analyzer. A particular diagnostic instrument is called QBC.RTM., and is sold by Becton Dickinson and Company, Franklin Lakes, N.J. That instrument includes a capillary tube containing a solid cylindrical plastic float. A patient's blood, the sample medium, is drawn into the tube, the tube end is sealed with a plastic cap and the tube spun in a microhematocrit centrifuge for five minutes. During centrifugation the plastic float having a specific gravity that is midway between that of the plasma and the red blood cells floats on top of the red blood cells and is surrounded by the expanded buffy coat. The float occupies more than 90% of the cross-sectional area of the tube and so the buffy coat is expanded ten-fold in the gap between the inside wall of the tube and the outside diameter of the float. The individual buffy coat layers have been easily measured but not automatically analyzed in a rapid manner by the technique disclosed herein. U.S. Pat. Nos. 4,567,754 and 4,190,328 disclose quantitative buffy coat tubes and the background in each patent is instructive on the slow procedures currently used to read buffy coat. Those background and disclosures are incorporated herein by reference.
The expansion of the sample medium in the gap between the bore of the capillary tube and the float is important in that the relative quantity of each component in the sample medium is a function of the gap volume or radial dimension. Therefore, the identical dimensions of each tube and float used when analyzing buffy coat is a concern.
U.S. Pat. No. 4,859,861 addresses optical techniques for measuring the bore diameter to high accuracy, allowing manufacture of tubing of a known bore. U.S. patent application Ser. No. 194,614, addresses an optical technique to directly measure the gap in a prepared QBC sample. In a fast, high accuracy, automatic QBC analyzer, it would be valuable to be able to simultaneously read the buffy coat and measure the gap dimension. This disclosure answers the need to give a fast, accurate, and automatic reading of the sample medium inside the gap formed between a precision bore capillary and its float therein, while simultaneously allowing practice of a U.S. patent application Ser. No. 194,614 U.S. Pat. No. 4,359,861.